Method of anchoring autologous or artificial tendon grafts in bone

ABSTRACT

An anchor assembly for autologous or artificial tendon grafts comprises an insertion element and a stabilizing element. The insertion element has a stem and a head containing an aperture large enough to receive a graft. The stabilizing element is adapted to be embedded in bone, and comprises a sleeve with a cavity arranged to receive and hold the insertion element stem. In use, the stabilizing element is affixed in the bone, and the stem of the insertion element is placed therein. A tendon graft may be secured to the insertion element either before or after its placement in the stabilizing element. Two such anchors may be linked with one or multiple grafts, in either a two-ply or four-ply arrangement.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 12/617,392 filed on Nov. 12, 2009, which is a divisionalapplication of U.S. patent application Ser. No. 10/623,212 filed on Jul.18, 2003, now U.S. Pat. No. 7,637,949, which is a divisional applicationof U.S. patent application Ser. No. 08/976,257 filed Nov. 21, 1997 (nowU.S. Pat. No. 6,616,694), which is a continuation-in-part of both U.S.patent application Ser. No. 08/887,580, filed Jul. 3, 1997 nowabandoned, and of U.S. patent application Ser. No. 08/754,566, filedNov. 21, 1996 now abandoned, the contents of which are incorporatedherein by reference in their entireties.

BACKGROUND OF THE INVENTION

This invention pertains to surgical systems and, more particularly,apparatus and methods for attaching autologous or artificial tendongrafts to bone. The invention has application in, for example, repair ofthe anterior cruciate ligament (ACL) of the knee. It may also be used,for example, for repair of other ligaments, such as of the elbow orankle.

It is not uncommon for ligaments and other soft tissue to tear or detachfrom bone. Athletes, for example, often suffer tears or other injuriesto the anterior cruciate ligament, one of the ligaments connecting thefemur. (thigh bone) and the tibia (shin bone) at the center of the kneejoint. The ACL, which limits hyperextension of the knee and prevents thebackward sliding of the femur on the tibial plateau, may be injured whenthe knee is twisted beyond the normal range of motion, e.g., when theknee is twisted while bending and weaving during skiing and other sportsactivities. ACL injuries may take the form of total or partial tears.

Reconstruction is the most common form of surgery for injuries to theACL and involves replacing the ACL with a graft of autologous orartificial tendon. An autologous tendon graft may be “harvested” fromthe patient's patellar ligament, which is part of the common tendon ofthe quadriceps femoris, connecting the patella to the tibia. Analternative autologous tendon graft may be harvested from thesemitendinosus tendon, which runs posteriorly and medially along thethigh and which connects the upper femur to the tibia.

Traditionally, patellar grafts are harvested with attached bone plugsthat can be securely fixed at the ends of a bone tunnel drilled throughthe tibia and femur using a metallic interference screw, a metal screwand washer, or buttons. Drawbacks associated with the use of thepatellar tendon-include difficulties in harvesting the tendon andpostoperative complications.

More recent success has been achieved using one or more strands of thetriple-stranded semitendinosus, tendon, which can be harvested withminimal-post-operative complications. The strands can be used alone orin combination with the gracilis tendon, which anatomically runsparallel along the thigh to the semitendinosus tendon. Althoughsemitendinosus tendons are increasingly used in ACL repair, they aredifficult to attach to bone, due in part to the absence of associatedbone plugs.

The art suggests, several techniques for attaching the semitendinosustendon to bone in ACL repair. One such technique involves suturing thetendon to a button or staple on the exterior of the bone. Drawbacksassociated with this method include stretching or failure of the suture,which may be subjected to tensile forces ranging from 30-50 pounds.

Another technique involves attaching a tendon graft to bone usingmetallic screws. Although such metal screws demonstrate stable fixationand good tensile strength, they have, a number of drawbacks. Theseinclude distortion of post-operative radiological studies, an allergicor rejection reaction resulting from metal sensitivity associated withpermanently implanted metal screws, and the potential need foradditional operations for removal or replacement.

Another technique involves attaching a tendon graft to an anchor affixedwithin a tunnel drilled in the bone. One anchor intended for this use isthe Mitek Ligament Anchor available from Mitek Surgical Products, Inc.That anchor includes prongs that lodge into the bone after the anchorhas been pulled into position by a suture. A drawback of that anchor isthat it must be lodged in the cortical layer near the surface of thefemur and therefore necessitates the use of long tendon segments. Inaddition, the anchor's design necessitates that it be fabricated frommetal to ensure sufficient holding strength.

An object of this invention is to provide improved surgical systems, andmore particularly, improved methods and apparatus for attachingautologous or artificial tendon grafts to bone.

Another object of this invention is to provide improved methods andapparatus for attachment of autologous or artificial tendon grafts(e.g., for ACL repair) that are in which the attachment means can befabricated from polymers or bioabsorbable materials, without the use ofmetals.

A related object of this invention is to provide methods and apparatusfor attachment of autologous and artificial tendons that minimize oreliminate the risk of graft pullout normally associated with ACL orother reconstructive orthopedic surgery.

SUMMARY OF THE INVENTION

The above objects are among those met by the invention, which providesimproved methods and apparatus for attaching autologous or artificialtendon grafts to bone, e.g., during ligament and other reconstructivesurgery, including ACL reconstruction. These allow anchoring the tendongraft in the bone, without metal and without placing undue load onsutures.

In one aspect, an assembly according to the invention comprises aninsertion element and a stabilizing element. The stabilizing element hasan outer surface adapted for interference fit with a bone hole. Theinsertion element includes an aperture through which a graft may bethreaded or attached, and a stem adapted to be inserted into andretained in a cavity in the stabilizing element, e.g., by aninterference fit. Additionally, the insertion element may comprise anaperture, slot, or barb, preferably at its distal end, to facilitate itsinsertion into the stabilizing element.

According to one aspect of the invention, the stabilizing element has athreaded outer surface that can be securely turned into the bone. Inaddition, the stabilizing element can have an inner bore that is smallerthan the outer diameter of the insertion element, such that placement ofthe latter into the former causes the stabilizing element to deformablyexpand or otherwise obtain a still stronger pressure fit with the bonehole.

In another aspect, the invention provides a stabilizing element that hasa flanged head that rests on the surface of the bone, outside of thebone hole, and that prevents the element from entering the bone holebeyond a certain point.

In further aspects of the invention, the insertion and stabilizingelements comprise bio-compatible materials. These avoid adversebiological reactions to the elements, as well as the need for a secondsurgical procedure to remove the elements.

A related aspect of the invention comprises a system comprising two ormore anchoring assemblies as described above. Such a system can be usedwith one or more natural or artificial crafts to repair or strengthen askeletal bone or joint. In ACL repair, for example, one stabilizingelement: can be placed at one end of a bone hole drilled into the femur,and the other stabilizing element can be placed in an aligned tunneldrilled into the tibia. The first and second insertion elements can thenbe joined by the graft and inserted into their respective stabilizingelements. The stabilization element placed in the femur can be of thetype having a threaded outer surface, while that emplaced in the tibiacan be of the type having a flanged head. Such a configuration exploitsthe strong cancellous matter in the femur, which is well adapted toholding screw threads, and relies on the surface of the tibia to ensurea hold there.

Another aspect of the invention comprises a method for anchoring a graftin bone, for example for the replacement of a torn ligament. In thismethod, a tunnel or opening is drilled into the bone, and astabilization element of the type described above is placed therein. Agraft is looped through the head of an insertion element which, in turn,is inserted into the stabilization element. The insertion andstabilization elements may incorporate various structures designed tomore effectively dispose and/or secure them in the bone tunnel, asdescribed above. For example, the stabilization element may comprise aflanged head which prevents it from being pulled into the bone tunnelwhen tension is applied to the tissue graft after insertion of theinsertion element.

In yet another aspect, the invention comprises a kit for securing agraft, e.g., for ACL replacement. The kit comprises two stabilizationelements adapted to be secured in bone. These can include, for example,a stabilization element adapted to be secured (e.g., in the femur) byscrew threads and a stabilization element adapted to be secured (e.g.,in the tibia) by a flange which prevents the element from being pulledthrough a bone hole. The kit further comprises two insertion elementsfor securing the graft to the stabilization elements. Each insertionelement is provided with an aperture at the head whereby an autologousor artificial tissue graft may be attached, as well as a stem adaptedfor insertion into a cavity in a stabilization element. These insertionelements may also comprise an aperture, slot, or barb, to facilitatetheir being pulled into the corresponding stabilizing element. The kitmay optionally include a graft, such as a length of artificial tendon ora length of actual semitendinosus tendon.

More generally, the invention also comprises a kit for connecting two ormore bones with grafts, for example, for replacing ligaments of theankle or elbow. In this aspect, the kit comprises at least twostabilization elements of the types described above of appropriate sizeand anchoring configuration for the bones in which they are intended tobe emplaced. The kit further comprises a comparable number of insertionelements of the types described above intended to be inserted into thestabilization elements, each of which comprises an aperture at the headsuitable for affixing a graft. The kit may optionally include one ormore lengths of artificial tissue, or it may be intended to be used withone or more autologous grafts.

Methods and apparatus of the instant invention overcome limitations ofprior art systems for affixing grafts to bone. The two-piece apertureddesign enables construction of an anchor assembly to attach autologousor artificial tendon grafts securely within bone without the use ofmetal, and without placing the high loads on sutures that are associatedwith sewing or tying grafts directly to bone.

Yet other aspects of the invention comprise methods for ligamentreconstruction, whereby various configurations of grafts are used toconnect bone anchors of the types described above, or other anchorscontaining apertures suitable for threading grafts. These methods employat least one graft having a filament extending from at least one of itsends. By way of example, this filament may be a suture which has beenwhip stitched to the end of a tendon graft.

The graft as emplaced according to this aspect of the invention mayconnect the bone anchors with two or four plies of graft material. Inone two-ply configuration, a single graft is used. The graft is threadedthrough the aperture of one bone anchor, and folded to bring its endsinto proximity. The two ends are then affixed to the other bone anchor,preferably by sewing with the attached filament(s). The anchors can beaffixed in bone before or after threading of the grafts.

A related method, according to the invention also employs a singlegraft. The graft is threaded through the apertures in both bone anchors,and the attached filament(s) are used to connect the two ends of thegraft to one another. This is preferably done by sewing the filaments ateach end of the graft to the other end of the graft.

Another method according to the invention uses a single graft to connecttwo bone anchors via four plies of graft material, rather than by twoplies as described in the previous two methods. According to thismethod, the graft (with at least one attached filament) is threadedthrough an aperture of a first bone anchor, and folded so that its endsare brought into proximity as described above. The two ends are thenthreaded through an aperture of a second bone anchor, and the graft isfolded again, to bring its ends in contact with the first anchor. Theattached filament(s) are used to connect the ends to the first anchor,preferably by sewing.

Other methods of attaching the grafts to bone anchors employ multiplegrafts. These methods can lend additional strength to the reconstructedligament. According to one such method, a graft with attachedfilament(s) is threaded through an aperture of one anchor and its endsare sewn to an aperture of another anchor, as described above. Inaddition, a second graft is threaded through the aperture of the anchorto which the first graft is sewn, and is sewn to the aperture of theanchor through which the first graft is threaded.

Another multiple-graft method of attachment threads two grafts (eachwith at least one attached filament) through the aperture of a boneanchor. The two grafts are folded, and their ends are attached to theaperture of a second bone anchor via the filaments. Each of thesemultiple-graft methods connects the anchors by four plies of graftmaterial.

These and other aspects of the invention are evident in the drawings andin the description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the invention may be attained byreference to the drawings, in which:

FIG. 1 a depicts a frontal view of the bones of the knee and a partiallytorn anterior cruciate ligament (ACL);

FIG. 1 b depicts a side view of a method for creating a stepped tunnelthrough the tibia and partially through the femur for insertion of ananchor assembly according to the invention;

FIG. 2 depicts a frontal view of a method for affixing a tendon graftinto the tunnel of FIG. 1 b in accord with the invention;

FIG. 3 depicts a detailed side view of an embedded anchor assembly ofthe present invention;

FIGS. 4 a-d depict detailed views of an anchor assembly of the presentinvention;

FIGS. 5 a-5 c depict detailed views of the insertion element of ananchor assembly according to an alternate embodiment of the presentinvention;

FIG. 6 depicts a detailed view of the insertion of an assembly accordingto yet another alternate embodiment of the present invention, thisembodiment comprising the use of two stabilizing elements and twoinsertion elements;

FIG. 7 depicts a detailed view of a stabilizing element comprising aflange;

FIG. 8 depicts a detailed view of a graft prepared for attachment to oneor more bone anchors; and

FIGS. 9 a-9 f depict detailed views of grafts linking two bone anchorsaccording to the methods of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 a depicts a partially torn ligament of the knee, e.g., theanterior cruciate ligament (ACL) 1. In the illustration, the ACL isattached to a depression in the anterior intercondylar area (not shown)on the surface of the tibial plateau 5. This tibial attachment lies infront of the anterior intercondylar tubercle and is blended with theanterior extremity of the lateral meniscus (not shown). It passesupward, backward, and laterally to be fixed into the posterior part ofthe medial surface of the lateral condyle (not shown) of the femur 3.The tibia 2 and the patella 4 are also shown.

FIG. 1 b depicts a method for creating a stepped tunnel 7 through thetibia 2 and partially through the femur 3 for insertion of an anchorassembly of the invention. In the illustration, a drill 6 is used by thesurgeon to drill a tunnel beginning at the anterior surface of the tibia2 and ending within the cancellous region of the femur 3. The drilltunnel 7 preferably will enter the femur 3 at or near the isometricpoint (not shown) close to the anatomical ACL attachment site inaccordance with the prior art. The angle of the drill tunnel is inaccord with that practiced in, the prior art for semitendinosus-styleACL repair. The stepped hole is formed by use of a stepped drill bitsuch that the ledge separating the wider and narrower diameter tunnelslies within the cancellous portion of the femur 3, e.g., within 10 mm to70 mm within the femur of the posterior part of the medial surface ofthe lateral condyle and, preferably, within approximately 45 mm of thatsurface. The drill tunnel 7 may terminate within the cancellous portionof the femur 3, or, in the alternative, the surgeon may elect initiallyto fully penetrate the femur 3 with a guide wire (not shown), leaving asmall exit aperture 9 on the opposing surface of the femur in accordancewith the prior art covering ACL reconstructive surgery. It will beappreciated by those skilled in the art that the above-describedinvention is not limited to embedding an anchor assembly in the femur 3but could also be practiced to embed an anchor in the tibia 2 or inbones comprising other joints, e.g., the ankle or elbow region, as wellas in individual or groups of bones otherwise requiring repair orsupport.

FIG. 2 depicts shows a graft anchor assembly 12 of the instant inventionembedded in bone, for example in the cancellous layer of the femur 3. Atendon graft 110 is looped through the aperture (see detailed drawing inFIG. 3) in an anchor assembly 12 with one or more free ends extendingthrough other bone, for example, through the tibia 2.

FIG. 3 depicts in more detail an anchor assembly 12 in operatingposition embedded in the stepped bone tunnel. The autologous orartificial tendon graft 10 is looped through aperture 13 in the head ofthe insertion element 14. The stabilizing element 15 is embedded in thebone tunnel, for example by screwing into the stepped tunnel. In anotherembodiment, the stabilizing element may be secured by means of a flangewhich opposes tension on the tendon graft, as shown in FIG. 6. Theinsertion: element 14 is held in the stabilizing element 15 for exampleby compression fit, but could also be held by other interference fit,e.g., screwing (though, preferably by a thread) that requires twist,e.g., of lot more than 180.degree. (so as to avoid twisting the tendon)or by ratcheting or by other attachment mechanism for holding oneelement in another without excessive twisting.

FIGS. 4 a-d depict the anchor assembly in detail. FIG. 4 a depicts thestabilizing element 15 which comprises an elongated sleeve 19 containingexternal protrusions 16, for example, external threads. Stabilizingelement 15 has a cavity 17; for example an elongated axial channel 17extending at least partway from the proximal end of stabilizing element15. For example, axial channel 17 could extend from the proximal to thedistal end of stabilizing element 15. Stabilizing element has a flangedhead 18. Stabilizing element 15 is comprised of a biocompatiblematerial, for example, implant grade high density polyethylene, lowdensity polyethylene (PE 6010 and PE 2030) and polypropylene (13R9A and23M2) all made by Rexene, Dallas, Tex. or of a bioabsorbable material,for example poly-1-lactide or such as a lactide-glycolide composition.It may also be comprised of a metal, such as surgical implant gradesteel.

FIG. 4 a also depicts insertion element 14. Insertion element 14 has anaperture 13 containing head 21 for retaining a ligament replacement.Stem head 21 has an aperture 13 of a size suitable for receivingmultiple strands of autologous and/or artificial tendon, but optimallyfor receiving two or more strands of semitendinosus tendon. The aperture13 may have dimensions 0.10 inches-0.35 inches (height) by 0.05-0.30inches (width), and, preferably approximately 0.220 inches by 0.160inches. Insertion element 14 has a stem 20, for example an elongatedstem 20. The stem has protrusions 22 extending outwardly: Stem,protrusions 22 may be inflexible. In the illustrated embodiment, thediameter of stem 20 has a larger outer diameter than the inner diameterof axial channel 17, such that stabilizing element 15 is capable ofholding the insertion element 14 by compression fit upon insertion ofthe insertion element 14 into channel 17 of stabilizing element 15. Theinsertion element 12 can be tapped into the stabilizing, element 15 withan emplacement device (not shown). Alternatively, the insertion elementcan be configured to be screwed, ratcheted or placed in otherinterference fit within the stabilizing element. The insertion element12 is comprised of a biocompatible material, for example implant gradehigh density polyethylene, low density polyethylene (PE 6010 and PE2030) and polypropylene (13R9A and 23M2: all made by Rexene, Dallas,Tex.) or of a bioabsorbable material, for example poly-1-lactide or suchas a lactide-glycolide composition, it may also be comprised of a metal,such as surgical implant grade steel.

FIG. 4 b depicts axial channel 17 which has a non-cylindricalcross-section (not shown), optimally a polygon such as a hexagon Othernon-cylindrical cross-sections such as a square or pentagon or even ovalconfigurations are also envisioned. A non-cylindrical cross-section ofthe axial channel 17 is designed such that a emplacement device (notshown) such as a driver (not shown) with a corresponding non-cylindricaldiameter can be inserted into a axial channel and turned such that theexternal threads 16 of the stabilizing element 15 are screwed into andgrip the bone. One such driver is, e.g., an Allen wrench.

FIG. 4 c depicts insertion of the distal end of an insertion element 12into the axial channel 17 at the proximal end of a stabilizing element15. The diameter of elongated stem 20 is slightly greater that thediameter of the non-cylindrical axial channel 17 of the stabilizingelement. As a result as depicted in FIG. 4 d, an elongated stem 20 ofthe insertion element 12 is held tightly in stabilizing element 15, forexample by compression fit into stabilizing element 15 embedded in astepped bone hole.

FIG. 5 a depicts an insertion element 10 that can be pulled into thestabilizing element 15 (FIG. 4). As above, the insertion element 10 hasan aperture 12 containing a head for retaining a ligamentreplacement—and a stem 14 with outwardly expanding protrusions. Thediameter of stem is greater than the diameter of axial channel such thatstabilizing element 15 is capable of holding the insertion element bycompression fit upon insertion of the insertion element into the channelof the stabilizing element. Additionally, the insertion element 10contains a structure, e.g., aperture 16, suitable for receiving asuture, a wire or other device that can be used to pull the element 10into the stabilizing element 15 instead of, or in addition to, its beingtapped into that element 15.

The aperture 16 or other such structure can be located at any point onthe insertion element 10 but is preferably located at the distal end ofthe insertion element. Thus, for example, in an embodiment in which thestem of the insertion element is approximately 0.75 inches long with adiameter of 0.16 inches, the aperture is located 0.05-0.20 inches fromthe end of the insertion element and preferably 0.12 inches from thedistal end.

The aperture 16 (or other such structure) is sized sufficiently toaccommodate a suture, wire or other pulling device. Those of ordinaryskill in the art will of course appreciate that in lieu of an aperture,a slot, barb, hook (as shown in FIGS. 5 b and 5 c) or any otherstructure by which the insertion element can be pulled, can be utilized.

An anchor assembly incorporating an insertion element 10 of FIG. 5 a isgenerally implanted as described above. In ACL reconstructive surgery,for example, a tunnel is drilled at the anterior surface of the tibiaand ending within the cancellous region of the femur. The drill tunnelpreferably enters the femur at or near the isometric point close to theanatomical ACL attachment site in accordance with the prior art. Theangle of the drill tunnel is in accord with that practiced-in the priorart for semitendinosus-style ACL repair. A stepped hole is formed by useof a stepped drill bit such that the ledge separating the wider andnarrower diameter tunnels lies within the cancellous portion of thefemur, e.g., within at least 10 mm to 70 mm within the femur of theposterior part of the medical surface of the lateral condyle and,preferably, approximately 45 mm of that surface.

Although the drill tunnel may terminate within the cancellous portion ofthe femur, a guide wire or K-wire is preferably used to fully penetratethe femur, leaving a small exit aperture on the opposing surface on thefemur. The stabilizing element is then embedded in the drilled bonetunnel, for example, by screwing it into the stepped tunnel. At thispoint, the K-wire (which is preferably equipped with an eyelet at itsend) is used to thread a suture through the skin, bone and through thechannel of the stabilizing element. The suture is then looped throughthe aperture, hook, barb, or slot, or other such structure in theinsertion element. The insertion element is then pulled into thestabilizing element using that suture. Those skilled in the art willappreciate that a wire, hook or other such apparatus can be used inplace of the aforementioned suture.

FIG. 6 depicts yet another embodiment of the invention, which employstwo stabilizing elements and two insertion elements In His embodiment, astepped tunnel is drilled in the bone, beginning at the anterior surfaceof the tibia 2 and ending within the cancellous region of the femur 3,similar to the tunnel depicted in FIG. 1 b. The surgeon may electinitially to fully penetrate the femur 3 with a guide wire 26, leaving asmall exit aperture 9 on the opposing surface of the femur in accordancewith the prior art covering ACL reconstructive surgery.

A first stabilizing element 15 is then inserted in the femoral tunnel ashas been described above. Insertion elements 12 and 24 are joined by alength of soft tissue 10, such as a tendon graft, and the firstinsertion element 12 is inserted into the stabilizing element 15, forexample by pushing into the stabilizing element 15, or by pulling with asuture, wire, or other device 26 on a small aperture, slot, barb or hookon the insertion element 12. The second insertion element 24 is pushedinto the bone tunnel, and then the second stabilizing element 28 isplaced-in the bone tunnel. In the preferred embodiment depicted in FIG.6, the second stabilizing element 28 comprises a flange 30 which limitsthe extent to which the stabilizing element can be pulled into the bonetunnel, e.g., by the tendon graft. This element is also depicted in FIG.7 and is further discussed below. In other embodiments, the secondstabilizing element may be secured by means of screw threads, aninterference fit, or other methods known in the art. Finally, the secondinsertion element 24 is inserted into the second stabilizing element 28.In the preferred embodiment depicted in FIG. 6, the second insertionelement is inserted into the second stabilizing element by pulling witha suture, wire, or other device 32 on a small aperture, slot, barb, orhook on the second insertion element 24.

In an embodiment for ACL replacement for an adult, the first stabilizingelement is typically of a length 20 mm, an outer diameter of 8 mm, andan inner diameter of 3.5 mm. The first insertion element is typically ofa length 40 mm and a diameter 8 mm. If the insertion element is equippedwith an aperture whereby it may be pulled into the stabilizing element,that aperture has a typical diameter of 1 mm. The aperture forattachment of the tendon graft is typically about 5 mm.times.8 mm. Thelength of the tendon graft between the insertion elements is usuallyabout 40 mm. Those skilled in the art will appreciate that the foregoingdimensions are supplied merely by way of example and that stabilizationand insertion elements of sizes suited for other bones, joints andgrafts can be used as well.

The surgeon can adjust the tension on the tendon graft by controllingthe extent to which the insertion elements are inserted into thestabilizing elements. Insertion elements are typically designed so thatfull strength hold of the insertion element in the stabilizing elementis obtained when the insertion element is inserted at least halfway intothe stabilizing element. Thus, the depth of each insertion element isadjustable over a length of 10 mm for this preferred embodiment.

The second stabilizing element 28 of FIG. 6 is also illustrated in FIG.7. This element comprises an elongated body 29, having a channel 31 forreceiving an insertion element. The stabilizing element also comprises aflange 30, which prevents the element from being pulled completely intothe bone hole by tension on a graft attached to an insertion elementdeployed in channel 31 The flange 30 may be perpendicular to theelongated body 29, or may be at an oblique angle to the body 29, asdepicted in FIG. 7 The flange 30 may also be contoured to correspond tothe shape of the outer surface of the bone in which it is to beemplaced. The surgeon may also elect to countersink the bone tunnel, sothat the outer surface of the emplaced flange 30 is flush with thesurface of the surrounding bone. In this embodiment, it may be desirablefor the flange 30 to be tapered, having a thicker cross-section at theintersection of the flange 30 with the body 29 than at the outer edge ofthe flange 30.

When this embodiment is used in ACL repair as depicted in FIG. 6, thesecond stabilizing element has a typical length of 15 mm, an outerdiameter of 8 mm, and an inner diameter of 3.5 mm. The flange has atypical outer diameter of 12 mm, and a typical thickness of 1 mm. Thesecond insertion element has a length 40 mm and a diameter 8 mm. If thesecond insertion element is equipped with an aperture whereby it may bepulled into the stabilizing element, that aperture has a typicaldiameter of 1 mm. The aperture for attachment of the tendon graft istypically about 5 mm.times.8 mm. Those skilled in the art willappreciate that the foregoing dimensions are supplied merely by way ofexample and that stabilization and insertion elements of sizes suitedfor other bones, joints and grafts can be used as well.

The second insertion element and second stabilizing element, like thefirst elements, are comprised of a biocompatible material, for exampleimplant grade high density polyethylene, low density polyethylene (PE6010 and PE 2030) and polypropylene (13R9A and 23M2) all made by Rexene,Dallas, Tex. or of a bioabsorbable material, for example poly-1-lactideor such as a lactide-glycolide composition. These elements may also becomprised of a metal, such as surgical implant grade steel.

It will be apparent to those skilled in the art that the above-describedinvention is not limited to connecting the femur and tibia in an ACLreconstructive procedure, but could also be practiced to support orrepair any bone or pair of bones with a length of soft tissue, e.g., inthe ankle or elbow region.

The invention further comprises methods for connecting at least two boneanchors, for example those described above, with one or more lengths ofgraft material. FIG. 8 shows a graft 10 prepared according to apreferred embodiment of this aspect. The graft 10 may be an autologoustendon graft such as a length of semitendonosis or gracillis tendon, oran artificial graft. The graft 10 has a filament 40 (such as a suture)attached to at least one of its ends. In the preferred embodimentillustrated in FIG. 8, a suture 40 is whip-stitched to each end of thegraft.

The anchors may be connected with one or with multiple grafts, in eithera two-ply or four-ply configuration. Some configurations according tothe invention are illustrated in FIGS. 9 a-9 f In FIG. 9 a, a singlegraft 10 is used to connect two anchors 42 and 44 in a two-plyconfiguration. A graft 10 prepared as illustrated in FIG. 8 is threadedthrough an aperture in one anchor 44, and then folded so that the twoends of the graft 10 can be tied and/or sewn to an aperture in the otheranchor 42 using the filament.

A related embodiment is illustrated in FIG. 9 b. In this embodiment, theprepared graft 10 is threaded through apertures in each of the twoanchors 42 and 44. The sutures 40 attached to the prepared graft arethen tied, or, preferably, sewn, to connect the ends of the graft 10.This embodiment is also a two-ply arrangement.

A four-ply connection between the anchors is achieved using a singlegraft in the embodiment illustrated in FIGS. 9 c and 9 d. A preparedgraft 10 is first threaded through one anchor 42, and folded to bringthe ends of the graft 10 into contact. These two ends are then threadedthrough the other bone anchor 44. FIG. 9 c illustrates the configurationof the graft at this point in its emplacement. The graft 10 is thenfolded in half again, to bring the ends back to the first anchor 42, andthe ends are sewn and/or tied there with the attached filaments 40, asillustrated in FIG. 9 d. Section A-A of that figure shows the four pliesof graft material 10 which now connect the bone anchors.

Other embodiments which achieve a four-ply connection between theanchors using multiple tendon grafts are illustrated in FIGS. 9 e and 9f. In the first of these, one graft 10, prepared as shown in FIG. 8, isthreaded through an aperture in a first anchor 44, and the sutures 40 atthe end of the graft are sewn and/or tied to an aperture in a secondanchor 42. A second graft 46 is then passed through the aperture in thesecond anchor 42, and sewn and/or tied to the aperture in the firstanchor 44 with its attached sutures 48. In the second embodiment,illustrated in FIG. 9 f, two grafts 10 and 46 are threaded through anaperture in the first anchor 44, and these two grafts are both sewnand/or tied to the aperture in the second anchor 42 with their attachedsutures 40 and 48.

It will be apparent to one skilled in the art of ligament reconstructionthat each of the embodiments illustrated in FIGS. 9 a-9 f has differentstrengths and that the preferred configuration for a particular use ofthe invention will depend on the ligament being replaced, the locationand type of the bone anchors, and on whether the graft is attached tothe anchors before or after they are affixed to the bone.

Described above are apparatus and methods meeting the objects set forthabove. Those skilled in the art will appreciate that the illustratedembodiments are shown and described by way of example only, and thatother, methods and apparatus incorporation modifications therein fallwithin the scope of the invention. For example, in addition to ACLreconstruction, the invention can be beneficially applied in connectionwith other soft tissue-to-bone attachments using bone tunnels, such as(by way of non-limiting example) repair of ligaments and tendons inother joints such as the elbow and ankle. In view of the foregoing.

1. A method of ligament reconstruction comprising: (a) extending afilament from at least one end of a graft having at least two ends; (b)threading the graft through apertures in each of a first and a secondbone anchor; (c) using the filament to affix the two ends of the graftto each other; (d) affixing the first anchor in bone; and (e) affixingthe second anchor in bone.
 2. A method of ligament reconstructioncomprising: (a) extending a filament from at least one end of a grafthaving at least two ends; (b) threading the graft through an aperture ina first bone anchor; (c) threading the two ends of the graft through anaperture in a second bone anchor; (d) using the filament to affix thetwo ends of the graft to the aperture of first bone anchor; (e) affixingthe first anchor in bone; and (f) affixing the second anchor in bone. 3.A method of ligament reconstruction comprising: (a) extending a firstfilament from at least one end of a first graft having at least twoends; (b) extending a second filament from at least one end of a secondgraft having at least two ends; (c) threading the first graft through anaperture in a first bone anchor; (d) using the first filament to affixthe two ends of the first graft to an aperture of a second bone anchor;(e) threading the second graft through the aperture in the secondanchor; (f) using the second filament to affix the two ends of thesecond graft to the aperture in the first anchor; (g) affixing the firstanchor in bone; and (h) affixing the second anchor in bone.
 4. A methodof ligament reconstruction comprising: (a) extending a first filamentfrom at least one end of a first graft having at least two ends; (b)extending a second filament from at least one end of a second grafthaving at least two ends; (c) threading the first graft through anaperture in a first bone anchor; (d) using the first filament to affixthe two ends of the first graft to an aperture of a second bone anchor;(e) threading the second graft through the aperture in the first anchor;(f) using the second filament to affix the two ends of the second graftto the aperture in the second anchor; (g) affixing the first anchor inbone; and (h) affixing the second anchor in bone.